Process and apparatus for the production of aerosols

ABSTRACT

A process and apparatus for production of aerosols which comprise charging a chemical in an aerosol forming apparatus equipped with a heating means and a fluid jet nozzle, and ejecting a fluid from the fluid jet nozzle, whereby a chemical vapor is drawn in the reduced pressure area formed by jetting of the fluid, as well as rapidly ejected into the atmosphere.

United States Patent 1191 Tanaka [11] 3,759,444 1451 Sept. 18,1973

[ PROCESS AND APPARATUS FOR THE PRODUCTION OF AEROSOLS Inventor: SeizoTanaka, Kanagawa, Japan Assignees: Showa Denko Kabushlki Kaisha,

Shiba-Tokyo; Sanko Kagaku Kogyo Kabushiki Kaisha, Tokyo, Japan Filed:June 21, 1971 Appl. No.: 158,671

Related U.S. Application Data Continuaiionbf Ser. No. 802,457, Feb. 26,1989, abandoned.

Feb. 28, 1968 Japan 43/13121 U.S. Cl. 239/138, 239/338 Int. Cl B05b 1/24Field of Search 239/138, 338

References Cited UNITED STATES PATENTS 3,511,236 5/1970 Conlin et a1.128/187 Foreign Application 1 W 3,097,645 7/1963 Lester 239/3381,999,265 4/1935 Tiscornia 239/138 2,181,650 11/1939 Briggs 239/1382,696,548 12/1954 Bencetti 239/138 X 3,398,897 8/1968 Urbanowicz..239/338 3,584,792 6/1971 Johnson 239/338 Primary Examiner-Lloyd L. KingAttorhey-Sughrue, Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT 9Claims, 3 Drawing Figures HEATING MEANS Pmminszmma 5.759.444

FIG. 3

PROCESS AND APPARATUS FOR THE PRODUCTION OF AEROSOLS CROSS-REFERENCE TORELATED APPLICATION BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention relates to a process for the formationof chemical containing aerosols and an apparatus for the same. Moreparticularly, it relates to a process and apparatus suited for theformation of aerosols of fungicides or insecticides.

The process of the present invention may be applied to a wide variety ofchemicals so long as they can be formed into aerosols. However, theprocess will be hereinafter explained in more detail with reference toits application to fungicides and insecticides which are the preferredembodiments.

2. Description of the Prior Art Recently, the application of fungicidesor insecticides in the form of aerosols thereof has received increasinginterest in the art and has been used with a wide variety of chemicalsas an effective means for controlling fungi and insects not only inenclosable rooms, such as warehouses and greenhouses, but also in openfields.

In general, processes for the application of insecticides or fungicidesin the form of aerosols, or atomized particles, can be classified asfollows:

A. Spraying a solution of active ingredients (e.g. fungicides,insecticides or both) which have been dissolved in a liquefied gasenclosed in a vessel utilizing the vapor pressure of the liquefied gas;

B. Spraying the solution of active ingredients using mechanicalatomization;

C. Vaporizing the active ingredients with a mixture combustible materialusing the heat of combustion; and

D. Vaporizing the active ingredients by indirect heating.

However, none of these known processes is completely satisfactory.Process (A) for instance, has drawbacks in (1) use of a liquefied gas inwhich the active ingredient is dissolved, (2) compression in a confinedcontainer, (3) the high cost of the liquefied gas as well as difficulthandling, etc. Process (B), though being rather widely used, still findslimited utility since it not only requires a particular solvent whichmust be.(1) inexpensive and (2) easily handled, but also the resultingaerosols are unstableand lack diffusibility and penetration into finespaces.

Processes (C) and (D) have been used in practical fields, for example,as formulations comprising a suitable mixture of active ingredients andcombustible materials such as sugars, zinc dust, aluminum dust, woodpowder, celluloid and similar organic materials, and optionally, with anadded oxygen-carrier such as salts or'esters of nitric acid, perchloratesalts, chlorate salts, bichromates, peroxides, etc. The processes arealso utilized by heating only the active ingredients by the heat of thecombustion. This is done by separating the combustible materials andoxygen-carrier, as illustrated above, from the active ingredients, andthen burning the separated combustibles. These two latter processes,

although advantageous in simple operation, also suffer from drawbacks.For examle, the effect of the active ingredient is considerably lowerduring the combustion or heating in an oxidative atmosphere, such asair, heating mixture, or hot combustion gas, due to the oxidativedecomposition of the active ingredient. Also, the by-products formedduring the combustion or heating of the active ingredient oftend havehazardous influences on humans, animals and plants.

Therefore, an improved process for the formation of aerosols of chemicalsubstances has long been desired in the art.

SUMMARY OF THE INVENTION It is an object of this invention to provide aprocess by which aerosols of chemicals, especially of fungicides,insecticides or mixtures thereof are formed in much more active statesthan those attained by prior processes.

Another object of this invention is to provide a process by whichaerosols of fungicides, insecticides or mixtures thereof are produced ata lower cost than in conventional processes.

A further object of this invention is to provide a process by whichaerosols of fungicides, insecticides or mixtures thereof are produced ina form containing much less decomposition by-prodlucts than priorprocesses which'are often hazardous-to humans, animals and plants.

Additionally, it is an outstanding advantage of this invention toprovide a high dispersion of pesticidal aerosols in an enclosed roomresultingin excellent control'of fungi and insects.

These objects have now been accomplished by the process of thisinvention, in which a pesticidal vapor is drawn into a reduced pressurearea formed around a jet nozzle by means of a fluid ejected at a highspeed into the atmosphere, virorouslymixed with air by the speed of jetstream, and rapidly cooled to cause formation of fine aerosols.

' BRIEF DESCRIPTION OF THE DRAWINGS The present-invention will beexplained in the followingby appended drawings,

The apparatus shown in FIG. 1 is an aerosol forming apparatus which isused in the case of the chemicals to be formed in aerosols beingcomparatively unstable in an oxidative atmosphere.

FIG. 2 shows an apparatus for use when the chemicals'utilized intheae'rosol are apt to decompose or dea grade in an oxidativeatmosphere, or the chemicals have low vapor pressures.

FIG. 3 shows a suitable apparatus for high vapor pressure, oxidationstable chemicals.

DESCRIPTION OF THE INVENTION This apparatus of FIG. 1 comprises acontainer 1 equipped with a heating device (which is shown schematicallyin the Figure) a cover 11 having a jet opening 12 and a bottom plate(13) of the container equipped with a fluid jet pipe 2 having a nozzle21. The chemicals to be formed in aerosols are charged in the bottomplate and heated to a prescribed temperature by means of the heatingdevice 14 of any suitable type. vaporized chemicals are drawn into thereduced pressure area formed by jetting the fluid from the nozzle andare immediately thrown out in the atmosphere to form aerosols.

In the apparatus of FIG. 2, the heating container is isolated from theopen air except for a gas suction opening which communicates with thereduced pressure area being opened to the container, in order to reducethe pressure of whole interior of the container, which acceleratesvaporization of ingredients and reduces the evaporation temperature toas low as possible. It will be easily understood that a nozzle is notalways directed upwards on the bottom of a heating plate, but a gassuction opening may open anywhere inside the container, in order toattain said object. By using this apparatus, vapor of chemicals is alsodrawn into the reduced pressure area, mixed rapidly with a jet stream,and further mixed strongly with the open air and cooled rapidly when thechemicals come out of the jet opening. Thus, it is possible toremarkably lower decomposition and deterioration by oxidation.

The apparatus of FIG. 3 has a simple structure, and is inexpensive andeasily handled, since the cover part is excluded from the apparatus asshown in FIG. 1.

It is preferable in any case that the jet pipe and the nozzle or thesuction opening of the pressure reduction device is positioned near theevaporation surface of heated chemicals. The chemicals do not stay onthe heating plate for long periods since the chemical vapor is drawninto the reduced pressure area formed by jetting fluid from the nozzleand forced therefrom and into the atmosphere. Accordingly, not onlystable aerosols in which deterioration of ingredient is very low areproduced, but, also it is possible to treat a large variety ofchemicals, as compared with those treated by a prior direct heating orpyrotechnic method. Further this process can be used for ingredientswhich are easily decomposable by controlling the reduced pressure in theheating container to low grade.

These facts will be apparent from the following description of variousprocesses for the formation of an aerosol of6-methylquinoxaline-2,B-dithiocarbonate (Morestane) useful as anagricultural fungicide.

EXAMPLE A An aerosol forming apparatus was set on the center of agreenhouse of 300m". Disinfection of cucumbers, on which powdery mildewwas parasitic, cultivated in the house was effected by natural diffusionof Morestane aerosols. The aerosol forming apparatus was a steel tray(container) having a diameter of 10 cm, without a cover, and wasequipped with a heating device. 30g of Morestane were charged into theapparatus, and the container was heated to 300C to form aerosols. As theresult, the germination control ratio for powdery mildew was only 73percent at the center of the house and the germination controllingeffect was hardly observed at outlying areas of the house.

' As the result of experiments on thermal decomposition of Morestanewhen forming aerosols, it was found that 47 percent by weight, based onthe Morestand used, was decomposed and remained in the apparatus. TheMorestane content in the aerosols product was only 34.5 percent, basedon weight of said collected aerosols.

EXAMPLE B Using a steel plate equipped with a heating device instead ofthe aerosol forming apparatus as described EXAMPLE C In anotherexperiment, cucumbers planted in a greenhouse of m, were disinfected byaerosols formed by burning a mixture comprising 20g of Morestane, 17g ofpotassium perchlorate, 30g of sucrose, 19g of charcoal powder, and 14 gof diatomaceous earth. As the result, there was no elimination ofpowdery parasitic mildew on the cucumbers, but also the cucumbers wereinjured by the decomposed chemicals.

EXAMPLE D On the contrary, according to the process of this invention,an aerosol forming apparatus as in FIG. 1 was placed on the center of agreenhouse of 300m? The apparatus comprised a steel open container 1having a diameter of 10 cm, a cover 11 having a jet opening(3cm/diameter) 12 in the center thereof, and a jet pipe 2 having anozzle 21 with an inner diameter of 0.8 mm disposed on the center of abottom plate 13 of the container. The jet pipe was inserted to a heightof 2 cm in the bottom plate, and the bottom plate can be heated byelectric heating. 30g of Morestane (M) was charged in container 1 andthe bottom plate 13 was heated to 300C, thus evaporating the Morestane.The vapor was drawn into the reduced pressure area formed by jetting airat a rate of 13 L./min. from the nozzle and thus rapidly ejected intothe atmosphere from the jet opening to form an aerosol, thus effectingdisinfection of cucumbers'planted in the house. The aerosol wasscattered throughout the whole of the house, and the germination controlratio for powdery mildew on the cumcumbers was 97 percent. In this case,the amount of Morestane decomposition products that remained in thecontainer was 14 percent by weight, based on the Morestane used, and theMorestane content in the aerosol was as high as 71 percent by weight.

Reasons for noxious insect and fungus extermination effect in theprocess of this invention as described above, can be explained asfollows: first, stable and diffusible aerosols are produced by theacceleration of fine atomizing since the vapor is drawn into the reducedpressure area produced near the nozzle, mixed violently with a jet fluidand ejectedinto and rapidly cooled by air; second, inactivation bythermal decomposition is restrained since the evaporation rate isaccelerated in accordance with the pressure reduction effect because thesupersaturated vapor at the heating surface is continuously drawn intothe reduced pressure area formed by a jet fluid; and third, diffusionareas are remarkably enlarged, as compared with the case when a jetfluid is not used since the aerosols are strongly ejected into anddiffused in the atmosphere together with the jet fluid.

In practicing the process of the present invention, since the degree ofpressure reduction formed by jetting can be easily varied, theevaporation rate of the ingredient can be controlled irrespective of thetemperature of the heating area. Consequently, it is easily possible toproduce aerosols of chemical substances having poor heat stability byincreasing the degree of pressure reduction, although the formation ofsuch aerosols was not possible previously, by heating to a temperaturebelow a decomposition temperature thereof. Furthermore, according to theprocess of this invention, it is possible to use a heating atmospherethat is oxygen free. Accordingly, it is thus even possible to produceaerosols of chemicals which are easily oxidized at the heatingtemperature.

As the jet fluid for producing the reduced pressure in the process ofthis invention, generally gas, liquefied gas, a mixture thereof andsmoke can be employable. Inert materials such as steam, carbon dioxideand nitrogen etc. are preferably used when the chemical substances areunstable. When chemical substances are comparatively stable, air ormethyl bromide gas can be used as the jet fluid. Although thetemperature of the jet fluid is not particularly important, it isgenerally from about room temperature to 100C. However, tem peratureshigher than 100C. may be used, unless deterioration of the chemicalsubstances occurs.

Although the heating temperature of the chemical substances cannot bespecified since it depends on heat stability, degree of pressureradiation, and volatility of the used ingredient, 600C. or less isgenerally used. 300C. or less is preferable when the heat stability ispoor.

The degree of pressure reduction used in the process of this inventiondepends on heat stability, vapor pressure, etc. of the ingredients.However, it is preferred that the degree of pressure reduction beincreased by using a closed apparatus if the heat stability of theingredients is poor, and/or vapor pressure thereof is low. In thismanner, it is possible to rapidly form aerosols without elevating theheating temperature. On the other hand, the closed apparatus is notnecessary if the vapor pressure is comparatively high and heat stabilityis good. In this case, increased noxious insect and fungus exterminationis obtainable by using an open contion, common heating method byelectric heat or fuel may be adapted.

The following examples are included as illustrative of the presentinvention.

EXAMPLE 1 An apparatus as in FIG. 2, consisting of a stainless steelcontainer 1 of a capacity of 100 cm", equipped with a jet pipe 2 havinga nozzle 21 of an inner diameter of 1 mm on a bottom plate of thecontainer and a gas suction opening of reduced pressure devicecommunicating with a jet opening 12 being opened to the container wascharged with 1g of sulfur, and was heated to 220C with jetting N atvelocity of 20L/min.

As a result, the vapor of sulfur was released in a carrier of N gasthrough the jet opening to the atmosphere without air flowing into thecontainer, and a stable aerosol was formed.

The amount of sulfur dioxide in the aerosol was only 1 weight percent ofthe used sulfur. On the contrary, when sulfur is heated on a hot plateat more than 240C, the sulfur was burned by flaming up, and there afteronly sulfur dioxide was obtained.

In forming aerosols on a heated plate to 220C, it was also confirmedthat 45 percent of the used sulfur was oxidized to sulfurous acid gas.

EXAMPLE 2 In an apparatus, as in FIG. 1, consisting of steel containerhaving a diameter of 10 cm and a height of 6 cm equipped with a jet pipeof inner diameter of 1.8 mm and a length of 1 cm at the center of thecontainer and a jet opening diameter of 4 cm at. the center of cover,the bottom plate of the container was heated by a methanol flame of260280C, and simultaneously steam was jetted through the jet pipe atvelocity of 20 L/min., 20g of 2,4-dichloro-d-orthoanilinotriazine mixedwith the same weight amount of bentonite were treated, and thereafterproduced an aerosol which was scattered to disinfect in a horticulturalglass house of 198 m in which cyclarnens were cultivated.

As the result, the percentage control of Botrytis cinerea on thecyclamens fell to 1.8 percent from 88 percent.

EXAMPLE 3 To cover of the apparatus used in Example 2 was removed, thecontainer charged with granule chemicals produced by mixing 30g ofy-hexachlorocyclohexane with 1.5g of dextrine, and heated to 250C. Theaerosol was then scattered about carnations cultivated in ahorticultural glass house of 396 m The air jetting was done at ambienttemperature and at a flow rate of 10 L/min.

As the result, the percentage control of aphides parasitic on thecarnations was 96 percent.

EXAMPLE 4 The apparatus of Example 1, consisting of steel container indiameter and 10 cm in height, equipped with jet nozzle of 2 mm in innerdiameter, was employed. A mixture of 30g ofN-trichloromethylthio-tetrahydrophthalimide with 10g of talc was chargedto the container, the cover sealed tightly, and the container heated to200250,C. Steam was jetted at velocity of 60 L/min. and thereaftercucumbers cultivated in a horticultural vinyl house of m were treatedwith the aerosol thus produced.

As a result, the percentage control of Erwinia aroideae was reduced toone eighth of that before treatement.

EXAMPLE 5 m Remarkably high prevention of the effect of powdery mildewon cucumbers and nematodes in the soil was obtained.

I claim:

1. Apparatus for the formation of aerosols from a said container openingto create a reduced pressure area adjacent said spraying means and todraw vaporized chemical into the fluid spray, whereby the vaporizedchemical is directed toward the container opening and cooled by contactwith the surrounding atmosphere to produce aerosols.

2. The apparatus of claim 1 wherein said conveying and spraying meanscomprise a fluid jet pipe having a nozzle.

3. The apparatus of claim 2 wherein said container has a bottom plateand said jet pipe and nozzle extend substantially upwardly from saidbottom plate.

4. The apparatus of claim 2 wherein said nozzle is positioned near theevaporation surface of said heated chemical in said container.

5. The apparatus of' asst;ifivnereiamatasaiaar has a cover with saidopening therein. V

6. The apparatus of claim 1 wherein said container has a cover with ajet tube extending into said container and defining said opening.

7. The apparatus of claim 6 wherein a shroud having openings for thevaporized chemical is connectedto the inner end of said jet tube, saidshroud surrounding said spraying means.

8. The apparatus of claim 1 wherein said chemical is a pesticide.

9. Apparatus for the formation of aerosols from a solid chemicalconsisting of a container for the chemical having an opening,

means for heating said container to a temperature sutflcient to"vapb'r'ize the chemical therein,

means for conveying a pressurized fluid into said container, and

means comprising a nozzle for spraying the pressurized fluid directlytoward said container opening and directly into the atmosphere to createa reduced pressure area adjacent said nozzle and to draw vaporizedchemical into the fluid spray emanating from said nozzle, said nozzlebeing positioned near the evaporation surface of the heated chemical insaid container, whereby the vaporized chemical is directed into theatmosphere in said fluid spray and cooled by contact with the atmosphereto form an aerosol.

1. Apparatus for the formation of aerosols from a solid state chemical,comprising a container for the chemical, said container having anopening, means for heating said container to a temperature sufficient tovaporize the chemical therein, means for conveying a pressurized fluidinto said container and means, including a nozzle, for spraying thepressurized fluid toward said container opening to create a reducedpressure area adjacent said spraying means and to draw vaporizedchemical into the fluid spray, whereby the vaporized chemical isdirected toward the container opening and cooled by contact with thesurrounding atmosphere to produce aerosols.
 2. The apparatus of claim 1wherein said conveying and spraying means comprise a fluid jet pipehaving a nozzle.
 3. The apparatus of claim 2 wherein said container hasa bottom plate and said jet pipe and nozzle extend substantiallyupwardly from said bottom plate.
 4. The apparatus of claim 2 whereinsaid nozzle is positioned near the evaporation surface of said heatedchemical in said container.
 5. The apparatus of claim 1 wherein saidcontainer has a cover with said opening therein.
 6. The apparatus ofclaim 1 wherein said container has a cover with a jet tube extendinginto said container and defining said opening.
 7. The apparatus of claim6 wherein a shroud having openings for the vaporized chemical isconnected to the inner end of said jet tube, said shroud surroundingsaid spraying means.
 8. The apparatus of claim 1 wherein said chemicalis a pesticide.
 9. Apparatus for the formation of aerosols from a solidchemical consisting of a container for the chemical having an opening,means for heating said container to a temperature sufficient to vaporizethe chemical therein, means for conveying a pressurized fluid into saidcontainer, and means comprising a nozzle for spraying the pressurizedfluid directly toward said container opening and directly into theatmosphere to create a reduced pressure area adjacent said nozzle and todraw vaporized chemical into the fluid spray emanating from said nozzle,said nozzle being positioned nEar the evaporation surface of the heatedchemical in said container, whereby the vaporized chemical is directedinto the atmosphere in said fluid spray and cooled by contact with theatmosphere to form an aerosol.